In a remarkable tableau at the White House, Obama, flanked by the leaders of Israel, the Palestinians and the only two Arab states with whom Israel has made peace, vowed to do everything within his power to achieve the comprehensive agreement that has eluded negotiators since Israel was established.

"We are but five men," Obama said. "Our dinner this evening will be a small gathering around a single table. Yet when we come together we will not be alone. We will be joined by the generations of those who have gone before and those who will follow."

"Do we have the wisdom and the courage to walk the path of peace?" Obama asked while looking at the four men seated next to the podium.

In somber, emotional tones, Prime Minister Benjamin Netanyahu of Israel and President Mahmoud Abbas of the Palestinian Authority expressed their own determination to make peace.

Netanyahyu, turning toward Abbas, called him his "partner in peace." He said he came to find a "historic compromise" but warned that any deal must ensure Israel's security.

Abbas, 75, said he would push hard despite "the difficulties we're going to face tomorrow." But he quickly foreshadowed the biggest early sticking point in the talks, calling for Netanyahu, 60, to freeze settlement activity in the West Bank.

The East Room gathering was a rare moment of diplomatic theater, endorsed by the attendance of President Hosni Mubarak of Egypt and King Abdullah II of Jordan and orchestrated by Obama as part of an effort to invest the process with his own personal stature. It came after Obama held a series of one-on-one meetings with the men throughout the day and just before they were to begin a working dinner. Netanyahu and Abbas begin direct talks today.

For Netanyahu and Abbas, the talks, with their very real chance of failure, represent a huge risk: President Bill Clinton's failed attempt in 2000 led to the Palestinian intifada , and President George W. Bush's Annapolis peace attempt dissolved amid chronic violence in Gaza.

"Too much blood has already been shed; too many hearts have already been broken," Obama said. "This moment of opportunity may not return soon again."

Obama assailed those responsible for the killings of four Israelis near the West Bank city of Hebron Tuesday. The terrorist Hamas movement, which rejects Israel's right to exist and opposes peace talks, claimed responsibility.

On Wednesday, Israeli police reported still another attack, saying Palestinian militants wounded two Israelis driving in the West Bank. Two people were reported injured, their car riddled with bullets.

The inclusion of Mubarak and Abdullah underlines the administration's hopes to forge a regional solution to the conflict. Egypt and Jordan are critical to providing Israel with security guarantees that would enable it to accept a Palestinian state.

Mubarak has offered to host subsequent rounds of talks in Egypt, although officials said he was pushing for Obama to take a direct personal role in the process. The standing of Mubarak, 82, in the region is such that officials said the administration was eager to get direct talks going quickly, because his health is said to be fragile and the United States is worried about the uncertainty that will come after he passes from the scene.

Jordan is a crucial player because of the difficult question of how to secure its border with a new Palestinian state. Israel has troops on that frontier and would balk at withdrawing them without a guarantee that the border would not become a conduit for missiles that militant groups opposed to the peace process, chiefly Hamas, could fire at Tel Aviv and other Israeli cities.

The success of the talks, all sides said, will depend in part on whether Obama can succeed in pushing Palestinians and Israelis toward resolving the core final status issues including the dismantling of Israeli settlements in the West Bank, the borders of a Palestinian state, the security of Israel, the status of Jerusalem and the fate of Palestinian refugees who left, or were forced to leave, their homes in Israel.

Obama will know quickly whether he has any more chance of success than the eight failed attempts before this one. At the end of September, Israel's 10-month moratorium on settlement construction will expire. Netanyahu so far has not indicated any willingness to extend it, and Abbas has said that he will withdraw from negotiations if settlement activity resumes.

The talks

• Issues involved: The Palestinian quest for statehood and Israel's insistence on an undivided Jerusalem as the Jewish capital.

• The goal: A deal in a year's time on the toughest issues that have sunk previous negotiations, including the borders of a new Palestinian state and the fate of disputed Jerusalem, claimed as a holy capital by both peoples.

• Today, the talks move to the State Department, under the eye of Secretary of State Hillary Rodham Clinton.